Illinois is facing a severe housing shortage. Governor Pritzker’s proposed BUILD Act is a critical first step, unlocking "missing middle" housing by allowing multi-unit developments on historically restricted single-family lots. Our analysis shows the base BUILD Act could unlock 1,176,054 new housing units across Chicago.
This proposal analyzes adding a Transit-Oriented Development (TOD) amendment similar to California's recently passed SB79.
We analyzed the Zillow Observed Rent Index (ZORI) to identify Chicago's top 15 neighborhoods experiencing the most extreme 5-year rent spikes. Under the base BUILD Act, only 7.1% of new citywide housing capacity falls within these critical high-cost areas, despite them comprising 12.5% of the city's residential land.
Why? Because the most desirable, walkable neighborhoods in Chicago are desirable because they are already dense.
In the Top 5 highest-rent-growth neighborhoods, 80.2% of the land is already zoned for multi-family housing.
Across the rest of Chicago, that number drops to just 32.1%.
Because land acquisition costs in these highly restricted neighborhoods are high, developers cannot afford to tear down a $1.5M single-family home just to build a 3-flat. To unlock housing in high-opportunity, transit rich areas, we must allow mid-rise density.
In the Top 5 most expensive neighborhoods, the base BUILD Act only upzones a potential 23,443 new units. Layering the CA SB79 transit density standard generates 129,651 units in those same neighborhoods.
By adopting a transit-oriented density model similar to California's SB 79, we can shift where housing gets built.
SB 79 effectively legalizes 5 to 10-story mid-rise apartment buildings, similar to the many courtyard buildings already built everywhere in Chicago, by guaranteeing baseline densities of 100 to 120 units per acre near high-frequency transit hubs. It overrides local exclusionary zoning and limits restrictive parking minimums, allowing dense, walkable communities in areas where the land values are highest.
If Illinois adopts a True CA SB 79 model allowing building near trains and bus intersections:
Upzoning allows building 2,443,083 units.
We unlock +1,267,029 additional homes compared to the base BUILD Act.
The share of new housing built in Chicago's 15 most expensive, highest-rent-growth neighborhoods nearly doubles to 13.5%.
Upzoning is also a fiscal boon. When we measure property tax yield per acre in Chicago's top 5 highest-rent neighborhoods, there is an obvious financial incentive for Transit-Oriented Development:
By allowing mid-rise buildings near transit, the city captures nearly 2.7x the tax revenue per acre compared to single-family homes, expanding the tax base without raising property tax rates on existing working-class homeowners.
Chicago's Affordable Requirements Ordinance (ARO) requires upzoned properties to designate 20% of units as affordable. This upzoning permits 245,436 new units strictly in the 15 most expensive neighborhoods. This amendment would mandate the private construction of 49,087 permanently affordable homes in areas with the city's best schools, transit, and job access while costing taxpayers zero dollars.
We analyzed four different legislative requirements for triggering transit-based upzoning. We compared the base SB79 text (upzoning units near Trains OR Bus Intersections) to alternatives requiring varying levels of access to transportation.
We calculated the following housing capacity increases for each proposal:
| Proposal Name | Nearby Transit Requirement | Total New Housing Units | Additional vs Pritzker |
|---|---|---|---|
| 1. Original Pritzker | Baseline "missing middle" upzoning applied evenly. | 1,176,054 | Baseline |
| 2. True CA SB 79 | Train OR intersection of 2+ high-frequency buses. | 2,443,083 | +1,267,029 |
| 3. Train Only | Strictly CTA/Metra rail stations. | 2,198,249 | +1,022,195 |
| 4. Train + Bus Options | Train AND (HF bus OR any 2 bus lines). | 2,036,943 | +860,889 |
| 5. Train + HF Bus | Train AND a 10-min frequency bus stop. | 1,751,978 | +575,924 |
Use the layer toggle on the interactive map below to switch between the different transit-oriented density scenarios and see exactly how housing capacity shifts across Chicago's neighborhoods.